Question

Which intervals are most appropriate for constructing a frequency table for the data set? 

Answer 1

There are a few criteria one can use for choosing intervals.

1. make the intervals as uniform as possible
2. cover the range in a "reasonable" number of intervals
3. appropriately reflect the data distribution
4. make the boundaries unambiguous

Selection B has boundaries that overlap, so can be ruled out immediately. Selection D has ranges that go from 19 to 9, so does not have very uniform intervals. Likewise, selection A defines the first interval to be twice the width of the others, so it isn't a good choice, either.

IMO, the best of the offered choices is ...

... C.) 20–34, 35–49, 50–64, 65–79